Curious as to whether herd immunity against the coronavirus disease 2019 (COVID-19) might slow the spread of the disease? Understand how herd immunity works and what experts are saying about its potential impact on the COVID-19 pandemic.

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Why is herd immunity important?

Herd immunity occurs when a large portion of a community (the herd) becomes immune to a disease, making the spread of disease from person to person unlikely. As a result, the whole community becomes protected — not just those who are immune.

Often, a percentage of the population must be capable of getting a disease in order for it to spread. This is called a threshold proportion. If the proportion of the population that is immune to the disease is greater than this threshold, the spread of the disease will decline. This is known as the herd immunity threshold.